This invention relates to an ultrasonic defect detection system, and more particularly to such a system which can detect location and/or size and/or orientation of a defect.
It is often desirable to know not just when a defect is located in a specimen such as a rail but also its size. Presently, the so called delta technique is used for this purpose. The delta technique slides an ultrasonic transmitter/receiver transducer along the front face of the rail directing a beam onto the rail at a fixed known angle for example 45xc2x0. Assuming the defect is transversely or vertically oriented the weak diffraction from the tips of the defect define a distance on the face of the rail. Using this distance and basic geometry, the size or height of the defect can be determined. However, this only applies when the defect is transverse or vertical. If it is not transverse or vertical, its orientation is unknown and its height or length or size will be indeterminate.
It is therefore an object of this invention to provide an improved ultrasonic defect detection system.
It is a further object of this invention to provide such an improved ultrasonic defect detection system which can determine any one or more of the location, size and orientation of a defect.
It is a further object of this invention to provide such an improved ultrasonic defect detection system which is effective regardless of the orientation of the defect.
It is a further object of this invention to provide such an improved ultrasonic defect detection system which does not require mechanical scanning.
It is a further object of this invention to provide such an improved ultrasonic defect detection system which can cover large inspection areas.
It is a further object of this invention to provide such an improved ultrasonic defect detection system which requires access to only one side of a specimen.
It is a further object of this invention to provide such an improved ultrasonic defect detection system which can be used automatically without a highly skilled operator.
The invention results from the realization that a truly simple and more effective ultrasonic defect detection system capable of determining any one or more of the location, size and orientation of a defect can be achieved with steered beam reflected off the back face of a specimen to create on the front face near and far shadows bracketing the defect and using the position of boundaries of those shadows to calculate location, size and orientation.
This invention features an ultrasonic defect detection system including a steered beam transmitter for directing an ultrasonic beam through the front face to the back face of a specimen. There is a sensor device for sensing the location on the front face of the near shadow of a defect from the beam reflected from the back face before the defect and the far shadow of the defect from the beam reflected from the back face after the defect. An arithmetic circuit responsive to the location of the shadows on the front face determines the distance between the transmitter and the near and far boundary of the near shadow and at least the near boundary of the far shadow for calculating the location of the defect.
In a preferred embodiment the arithmetic circuit may also calculate the size of the defect and may also calculate the orientation of the defect. The transmitter may include an ultrasonic phased array transducer. The transmitter may include a variable angle ultrasonic wedge transducer. The sensor device may include an interferometer. It may be a laser interferometer. The sensor device may include a piezoelectric receiver array. The arithmetic circuit may include a microprocessor. The arithmetic circuit may calculate the location of the defect using the expressions:             x      0        =                  1        2            ⁢              (                                                            x                A                            ⁢                              x                D                                                                    x                A                            +                              x                D                                              +                                                    x                B                            ⁢                              x                C                                                                    x                B                            +                              x                C                                                    )                        y      0        =          L      ⁡              (                                            x              A                                                      x                A                            +                              x                D                                              +                                    x              B                                                      x                B                            +                              x                C                                                    )            
The invention also features an ultrasonic defect detection system including a steered beam transmitter for directing an ultrasonic beam through the front face to the back face of a specimen. A sensor device senses the location on the front face of the near shadow of a defect from the beam reflected from the back face before the defect and the far shadow of the defect from the beam reflected from the back face after the defect. An arithmetic circuit responsive to the location of the shadows on the front face determines the distance between the transmitter and the near and far boundary of the near shadow and at least the near boundary of the far shadow for calculating the size of the defect.
In a preferred embodiment the arithmetic circuit may calculate the location of the defect and may calculate the orientation of the defect. The arithmetic circuit may calculate the size of the defect using the expression:   b  =                                          x            A            2                    ⁡                      (                                          4                ⁢                                  L                  2                                            +                              x                D                2                                      )                                                (                                          x                A                            +                              x                D                                      )                    2                    +              2        ⁢                  x          A                ⁢                  x          B                ⁢                                            4              ⁢                              L                2                                      -                                          x                C                            ⁢                              x                D                                                                        (                                                x                  A                                +                                  x                  D                                            )                        ⁢                          (                                                x                  B                                +                                  x                  C                                            )                                          +                                    x            B            2                    ⁡                      (                                          4                ⁢                                  L                  2                                            +                              x                C                2                                      )                                                (                                          x                B                            +                              x                C                                      )                    2                    
The invention also features an ultrasonic defect detection system including a steered beam transmitter for directing an ultrasonic beam through the front face to the back face of a specimen. A sensor device senses the location on the front face of the near shadow of a defect from the beam reflected from the back face before the defect and the far shadow of the defect from the beam reflected from the back face after the defect. An arithmetic circuit responsive to the location of the shadows on the front face determines the distance between the transmitter and the near and far boundary of the near shadow and at least the near boundary of the far shadow for calculating the orientation of the defect.
In a preferred embodiment the arithmetic circuit may also calculate the location of the defect; the arithmetic circuit may also calculate the size of the defect. The arithmetic circuit may calculate the orientation of the defect using the expression:   φ  =            tan              -        1              ⁡          (                                                  x              A                        ⁢                                          x                B                            ⁡                              (                                                      x                    C                                    -                                      x                    D                                                  )                                              -                                    (                                                x                  A                                -                                  x                  B                                            )                        ⁢                          x              C                        ⁢                          x              D                                                2          ⁢                      L            ⁡                          (                                                                    x                    B                                    ⁢                                      x                    D                                                  -                                                      x                    A                                    ⁢                                      x                    C                                                              )                                          )      
The invention also features an ultrasonic defect detection system including a steered beam transmitter for directing an ultrasonic beam through the front face to the back face of a specimen. A sensor device senses the location on the front face of the near shadow of a defect from the beam reflected from the back face before the defect and the far shadow of the defect from the beam reflected from the back face after the defect. An arithmetic circuit responsive to the location of the shadows on the front face determines the distance between the transmitter and the near and far boundary of the near shadow and at least the near boundary of the far shadow for calculating the location, size and orientation of the defect.